8.3 Ip traffic encapsulator

As a second example of a detailed route, let’s consider IP protocol route encapsulation in the Frame Relay. Using of high-level TCP (Transmission Control Protocol) protocol for IP traffic transmitting is shown on the route. The TCP protocol supplies controlling of IP data transmission.

Route 3 An example of the detailed route of IP encapsulation into the Frame Relay protocol (ParaScope 2000 analyzer)

DCE Frame 4 (47 bytes) was captured with no errors.

T1. 618:

Dlci c/r de becn fecn ea

103 0 0 0 0 0/1

RFC 1490:

Control = UI

NLPID = Internet IP

IP:

Version = 4, IP Header Length (bytes) = 20

Precedence = Routine

Type of Service = Normal Service

Packet Total Length = 41

Identification = 14200

DF Flag = Don't Fragment, MF Flag = Last Fragment

Fragment Offset = 0

Time to Live = 62

Protocol = TCP

Header Checksum = 72 B7

Source Address = 130.45.1.17, Destination Address = 130.45.141.52

TCP:

Source Port = 23 (Telnet), Destination Port = 1029

Seq Number = 338684219, Ack Number = 89351

Data Offset (bytes) = 20

Flags = ACK PSH

Window =4927

Header Checksum = 62 5D

Urgent Pointer = 0

Information:

02Ch: 49

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

DCE Frame 6 (47 bytes) was captured with no errors.

T1. 618:

Dlci c/r de becn fecn ea

103 0 0 0 0 0/1

RFC 1490:

Control = UI

NLPID = Internet IP

IP:

Version = 4, IP Header Length (bytes) = 20

Precedence = Routine

Type of Service = Normal Service

Packet Total Length = 41

Identification = 14205

DF Flag = Don't Fragment, MF Flag = Last Fragment

Fragment Offset = 0

Time to Live = 62

Protocol = TCP

Header Checksum = 72 B2

Source Address = 130.45.1.17, Destination Address = 130.45.141.52

TCP:

Source Port = 23 (Telnet), Destination Port = 1029

Seq Number = 338684220, Ack Number = 89352

Data Offset (bytes) = 20

Flags = ACK PSH

Window = 4926

Header Checksum = 58 5C

Urgent Pointer = 0

Information:

02Ch: 53

The address field of a Frame Relay message frame contains the address information (DLCI = 103). Information field starts with a control field header Q.922 and identification of UI message. Then there is the identifier of NLPID = Internet IP. IP Information message begins with a 20-octet IP header, followed by TCP message, and then the transmitted information in a 16-hex format.